1. Field of the Invention
This invention relates to an improvement in and relating to a solenoid operated poppet type change-over valve.
2. Description of Prior Art
Various kinds of solenoid operated poppet type change-over valves ae known. For example, U.S. Pat. No. 3,559,686 discloses one type of such conventional valves. In the device disclosed therein, when a solenoid coil is energized to attract an armature toward a solenoid frame, a valve member is displaced so that one closure member of the valve member is brought into abutment against the valve seat and the other closure member is spaced from its valve seat, thus turning the valve into a change-over position of the fluid flow passages. On the other hand, when the solenoid coil is de-energized to extinguish the electromagnetic force between the armature and the frame, the valve member returns to its original state due to the function of the return spring. The armature is spaced from the frame, and the original state of the intercommunication of the fluid flow passages is restored.
In this connection, a seal member is mounted on the side of a valve casing in the device disclosed in the above-mentioned prior publication. However, it is apparent that the seal member may be mounted on the side of the confronting valve member instead.
The prior valve has a V-shaped seal member which is adapted for hermetically sealing the valve chamber and for securely guiding sliding movement of the supporting rods of the valve member. In order to attain good sliding of the valve member without tilting, a stiff and rigid material must be used as the seal member. However, soft material must be used as the seal member in order to eliminate resistance against its sliding movement. This constraint gives rise to an adverse effect in that the valve member is apt to move with a tilted posture. The tilting of the valve member can also be caused by frictional wear of the seal member when used over a long period of time.
If the valve member is displaced while tilted, the closure members will naturally be in contact with the valve seat in an inclined and unstable state. Accordingly, various drawbacks will be generated, such as uneven seating of the closure member against the valve seat, failure to obtain a hermetic seal due to uneven engagement of the closure member with the valve seat, and partial abrasive wear of both the valve member and the valve seat.